Method and apparatus for positioning a dowel

ABSTRACT

SUPPORTS ARE ERECTED AT OPPOSITE SIDES OF A TOOTH CAVITY IN A DENTAL IMPRESSION AND A BRIDGING MEMBER, FRICTIONALLY MOUNTED ON SAID SUPPORTS, SPANS THE CAVITY AND SUPPORTS A DOWEL IN SELECTED POSITIONING IN THE CAVITY WHILE A CAST IS BEING POURED AND SET.

Jan. 12,1971 ;w

v I METHOD AND APPARATUS FOR POSITIONING A DOWEL Filed Sept. 9, 1969IlIR Wm M MW W3. it H United States Patent 3,553,839 METHOD ANDAPPARATUS FOR POSITIONING A DOWEL Kenneth W. Gores, 1026 112th NE.,Bellevue, Wash. 98004 Filed Sept. 9, 1969, Ser. No. 856,394 Int. Cl.A61c 13/00 US. CI. 32-11 Claims ABSTRACT OF THE DISCLOSURE Supports areerected at opposite sides of a tooth cavity in a dental impression and abridging member, frictionally mounted on said supports, spans the cavityand supports a dowel in selected positioning in the cavity while a castis being poured and set.

SUMMARY OF THE INVENTION A feature of the invention is the provision ofa simple method of locating and positioning a dowel in a tooth cavity ofa dental impression. The method is easily practiced to produce veryaccurate results without requiring the exercise of great skill on thepart of the operator. A dental impression usually formed of rubberlike,semi-elastic material is normally created in a formretaining tray. Apair of supports are disposed upright in the impression material atopposite sides of atooth cavity in said impression. Preferably thesupports are driven into the impression material. A flexible bridgemember is frictionally mounted adjacent its ends on said supports. Theflexible bridge member has at least one opening, in the preferred formof the invention, on its underside. A tapered dowel, to be embedded instone or plaster cast in the tooth cavity, has its upper tapered endinserted firmly into said opening whereupon the dowel depends into thecavity. An initial pour of casting material is made to a depthsufficient to partially embrace the lower end of the dowel. Then theupright supports and bridge member are removed. The upper end of thedowel is capped with a soft plastic cup-like member. A second pour ofcasting material is then made to embed the dowel to or slightly abovethe dowel cap. When the stone is hardened, the dowel cap may be removed.The operator may then remove his cast model from the impression and cutinto it from beneath to sever the dowelled tooth from the remainder ofthe model to the depth of the first casting. Then the operator strikesthe exposed upper end of the tapered dowel causing the dowel to slip outof the second casting, and to cause the first portion case to separateas a tooth unit. The dowel insures that the tooth unit may be accuratelyreturned to its normal position in the model.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the dowelpositioning apparatus;

FIGS. 2 and 3 illustrate, respectively, a dowel positioned according tothis invention, and a dowel as initially cast in the dental impression.

FIG. 4 illustrates a dowel as prepared for a second casting;

FIG. 5 shows the two-part cast model about to be parted to separate adowelled tooth unit; and

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FIG. 6 is a plan view of an impression tray showing the apparatus ofthis invention as in use.

DESCRIPTION OF THE INVENTION In an impression tray 10 having handle 11is placed a quantity of rubber-like, moldable, elastomeric material.This is then introduced into a dental patients mouth and firmly pressedagainst the dentition of one or the other of his jaws. The result is aresilient dental impression 12, i.e. a negative, from which a plastermold or model of the patients jaw and teeth may be reproduced. The usualpractice is to fill the cavities and contours of the impression bypouring and vibrating a plaster mix throughout the impression. Moderndental practices make it desirable that individual teeth of the model beseparable. For this purpose a dowel or pin is in the model so that, whenthe model has hardened, the operator by careful cutting may separate aparticular tooth from the model; however, still retaining means wherebyit may be accurately replaced. The single removable tooth model servesas a support or die around which artificial teeth, caps, crowns, andother prosthetic devices may be designed and produced. It is oftennecessary to remove and replace such a tooth model many times.

The practice of this invention involves the method of using apparatus ofthe nature shown in the FIG. 1 where there is a pair of sharp-pointedpins 14, 16, a bridging member 18, and a dowel 20. Preferably the pins14, 16 are T-headed for easy manipulation in placing them in position inthe impression 12.

A bridging member 22 is mounted adjacent its ends on pins 14, 16.Desirably member 22 is formed of plastic material, such as vinyl or thelike, as a series of small, hollow cylinders joined in side-by-siderelation. The cylinder passages provide several selective positions onpins 14, 16 and, from beneath dowel 20 may have its smaller endinserted. It is preferable that the bridge member 22 be mounted on onepin, say pin 14, farther from its sharpened end than is the case withpin 16.

The operator, upon superposing an assembly as shown in FIG. 1 over attray 10 containing an impression 12, will initially insert the lower pin14 into the impression margin. This establishes a pivot point. He maythen swing the pin 16 (see FIG. 6) in an accurate path selecting anappropriate location in the opposite impression margin suitable tosuspend the dowel 20 approximately at the axis of tooth cavity 30 in theimpression. Thereupon both pins 14 and 16 are pressed deeper into theimpression material so that they are held firmly erect. The operator maythen adjust the vertical disposition of dowel 20 relative cavity 30 byraising or lowering bridge member 22 on pins 14, 16.

When the apparatus has been suitably positioned, as in FIG. 2, plasteris poured into cavity 30 to fill the same sufficiently to engage thedepending knurled end 21 of dowel 20 as shown in FIG. 3. When thisinitial plaster model 34 has hardened, bridge 22 is disengaged from theupper end of dowel 20 and pins 14 and 16 are removed and laid aside.

Dowel 20 is next capped by a small plastic cup 32 as shown in FIG. 4whereupon additional plaster 36 is poured or applied over model 34 asseen in FIG. 5, there tending to be a parting line 38 there-between.Desirably the second pour does not cover cap 32 which upon re- 3 movalwill leave a small recess surrounding the upper tip of dowel 20.

The operator may then saw or otherwise cut away a dowelled toothimpression to a depth indicated by dotted line 40 in FIG. 5. A sharpblow as by punch 42. on dowel 20 will cause the tooth impression 40 toseparate from the remainder of the model, the dowel 20 easilywithdrawing by reason of its taper from cast portion 36.

While the foregoing discloses and describes the preferred form of theinvention, it will be apparent to those skilled in the art that changesand modifications may be employed Without departing from the spirit ofthe invention.

What is claimed is:

1. The method of positioning a dowel in a tooth impression cavity of adental impression, comprising:

erecting upright parallel pairs of supports rising from said impressionat opposite sides of a selected tooth impression cavity;

slidably and frictionally mounting a bridging member on said supports inspanning relation above said cavity; and suspending a dowel from saidbridge member into said cavity so as to facilitate vertical adjustmentof said bridging member.

2. The method of claim 1 in which the upright supports are erected bydriving the same into marginal portions of said dental impressionexternal of said selected tooth impression cavity.

3. Apparatus for positioning a dowel pin relative to a tooth impressioncavity of a dental impression, comprising:

a parallel pair of upright pins inserted into and supported by thedental impression material at opposite sides of a tooth impressioncavity therein; and

a bridging member slidably mounted on and spanning between said uprightpins traversing said cavity so as to be vertically adjustable relativeto said cavity;

said bridge member having at least one socket opening to receive andsupport a dowel in depending relation between said pins, and into suchtooth impression cavity.

4. Apparatus according to claim 3 in which said bridging member isformed of resilient material and there is a row of openings on itsunderside to variously receive and support a dowel.

5. Apparatus according to claim 4 in which the bridging member comprisesa series of open-ended hollow cylinders joined in side-by-sidesequential arrangement.

References Cited UNITED STATES PATENTS 6/1966 Kersten 249-205 9/1969IStern et al 32-17

